The "next big thing" or whatever will be a game that doesn't follow this formula:
Step 1: Start at level 1
Step 2: Do Quests like WOW etc.
Step 3: Supplement Step 2 with "Dynamic Events" which is just a silly term for randomly generated or locally scripted short term repeated events (See Rift and GW2).
Step 4: Supplement Step 2 and 3 with shitty hallway, trash-boss-trash-boss dungeons.
Step 5: Reach Max Level
Step 6: Do Heroic aka "hard mode" versions of Step 4. This allows you to access Step 7.
Step 7: Raid 10, 20, 25 Man Dungeons.
Now you can add all sorts of flavor to this formula, but it will never make the game stick. Type of flavor are:
- Battleground PVP
- WvW PVP
- Crafting
- Pet Battles
- Achievements etc.
Now PVP can make a game stick if you build a way to promote it. This is what GW2 failed to do. There are no ladders, points, leaderboards or any other way to show off. In a game with mostly horizontal gear treadmills, you need to a way to show off your epeen to others, and the look of your gear is not really the way, because most of the time people only notice it when you're idle.
That's how you fix Battleground, or instanced, pvp and probably WvW too to some degree.
W3 can be fixed by inputting a more permanent aspect to it, even if it's erased one a week. Instead of running around the same map every single week fighting people in the same strats, you really need to add wall and base building like an RTS.
The rest on the list above are just extras that add to the game but never really make it successful. They make great additions though.
TLDR: Get rid of levels, get rid of dungeon grinds.
If I were making a game today this is what I'll do:
Make a PVP focused game, full loot.
Three sides (maybe two).
Max 100-200 people online per side. The smaller the community, the more you're able to become notorious to feed the peen.
Server wide top 20 leaderboards. One for PVE and one for PVP. PVE is 90% gearscore and 10% PVP achieves. PVP is all about kills or "Honor totals" or whatever scores. Build the network so once a week the top 5 players of each server can enter in an automated tournament for bragging rights and more leaderboards.
Figure out some solutions for dying servers or overbalanced servers.
No instances.
Gear is dropped at as a % of a kill. Uber rare weapon has a 1% load chance on a 20% pop mob. Has a chance to load every time a zone "resets", which could be ever 10 minutes or every day. Whatever. Common items have a 90% chance to drop. This is a combo of Diablo style loot and typical loot rules. If it could be done, NPCs would drop what they wear so you can "see" the loot on an NPC before you attack it. So if all your orcs are wearing greyish plate they drop greyish plate, but 5% of the time one will load with a reddish plate that's awesomer. You will see this.
Those are the basics. I've elaborated on the more detailed design elements before.